The size of crowds in Berkeley protesting the killings by police of unarmed black men skyrocketed Monday night along with arrests.
Authorities say the number of those demonstrating against grand jury decisions in the deaths of Eric Garner and Michael Brown tripled from previous days. As many as 1,500 people demonstrated, and arrests rose to 159 as protests turned violent for a third night in a row.
Over the course of the night, protesters threw rocks, a train station was closed down and demonstrators blocked all lanes of Interstate 80, officials said.
"The California Highway Patrol is sworn to protect the peoples' right to peacefully assemble and demonstrate, however, the freeway is not the place to express one's opinions," the CHP said in a statement after demonstrations turned violent for the third consecutive night.
Over the weekend, the size of the protests topped out at about 600, according to the CHP. Groups of protesters occupied Interstate 80 while others allegedly threw bottles and rocks at officers.
Berkeley Mayor Tom Bates issued a statement Monday that said the previous nights' violence was "unacceptable."
"While the overwhelming majority of the demonstrators were nonviolent, we have had numerous reports of masked demonstrators as the main perpetrators of the damage and destruction," Bates said. "We don't know who they are, but they are not welcome in Berkeley."
City officials called for peace, but as protests wore on Monday night, those calls went unheeded.
Officials said Monday's incidents began when about 1,000 to 1,500 people began peacefully marching through downtown Berkeley at about 5 p.m. They stopped at the Berkeley Police Department, where officers in riot gear blocked them from nearing the building.
The protesters then moved on to a Bay Area Rapid Transit subway station, where demonstrators stood outside. BART officials closed the station for about two hours as a preventive measure, according to Lt. Gil Lopez of the BART police.
"We just had reports that a large group was coming toward our station," Lopez said. "It was preemptive."
Authorities said protesters then divided into smaller groups. In one incident, demonstrators were marching west on University Avenue toward Interstate 80 shortly after 8 p.m. when a small group entered the freeway through an opening in a fence, California Highway Patrol Officer Daniel Hill said.
By 8:30 p.m., he said, protesters had destroyed the fencing along the south side of the freeway at Aquatic Park and were flooding all the traffic lanes after the CHP shut down the University Avenue exit ramps.
"As officers attempted to stop the crowd and clear the freeway, the protesters became violent," Hill said, "and on several occasions assaulted CHP personnel with rocks and other objects."
The CHP arrested at least 150 people for various charges including resisting arrest, and Berkeley officers arrested nine others, including one juvenile.
Staff writer Matt Hamilton contributed to this report.